"Lazy" is a complicated term and can be used to describe a lot of different behaviours. In terms of energy levels, adolescents are going through a lot of changes physically, emotionally, and cognitively, and these changes can leave them tired and sluggish. Some studies have also shown that teens tend to have different circadian rhythms than their parents and younger siblings resulting in them not being able to fall asleep until much later, resulting in less sleep if they need to get up for school early in the morning. Teenagers need about nine hours of sleep per night and if they can't fall asleep until well after midnight, getting up at six or seven means they are likely to suffer from chronic sleep deprivation. If they are constantly getting insufficient sleep, your adolescent is likely to be sluggish, cranky and lethargic which can lead to conflict in the home over expectations for completing chores and homework or participating in activities etc... For more info about teens and sleep, check out this mayo clinic site: http://www.mayoclinic.com/health/teens-health/CC00019
In terms of what you can do about your teenager's lack of energy, encouraging healthy sleeping habits such as limiting or cutting off caffeine consumption in the later afternoon, maintaining regular bedtime routines, keeping TV's and other electronic devices out of the bedroom, getting sufficient exercise during the day, and trying to go to bed at the same time each night, can help to some extent but won't solve the problem entirely. Allowing the teen to catch up on sleep on the weekends and being understanding when he or she wakes up tired, groggy and possibly out of sorts can also help. Many parents see adolescents' sleeping in or difficulty getting up on time as an act of defiance when often it is simply that they are not getting enough sleep. Being supportive and understanding won't make him or her less sleepy but it can go a long way to making morning routines more peaceful.
Other accusations of laziness can come from adolescents' reluctance to interact with their family as they used to, increased defiance over chores or household expectations, or a desire to spend time alone. While these types of behaviours can, in a minority of cases, indicate deeper problems most of the time they are part of the normal growing pains of getting older, developing a sense of self, and individuating themselves from their family. This process can be difficult not only for the teen but also for their parents and siblings and when facing conflict over expectations and activities, teens may simply choose to do 'nothing' or complain about being 'too tired' as a way of explaining their actions, albeit in a somewhat passive aggressive manner. At that this stage, teens may also assert their independence and evolving personal preferences by choosing to no longer participate in certain organized activities like sports, dance, clubs or hobbies. Some parents feel these decisions reflect laziness or lack of commitment but often they are the result of a desire to prove they are an individual with power over their own life, a change in interests, a desire to try new activities, or a combination of these factors.
If you are concerned about your teenager's energy levels take a moment to reflect upon the situations in which he or she complains of being tired. Are mornings the problem? Is he or she exhausted by the end of the school day? Is it a response to spending time with the family or participating in specific activities? Is there a pattern to the incidences of 'laziness'? Talking to your teen may also offer insight into what's going on as well as giving you a chance to maintain open communication and show empathy for what your son or daughter is going through. Many families get locked in patterns of conflict and rebellion which can escalate but sitting down and calmly discussing the problem at a time when you are not currently engaged in conflict over it (i.e. not first thing after you had to drag her out of bed or directly after a fight over chores etc..) can give you both the chance to express how you feel and work together to find a mutually agreeable compromise.